In the majority of patients in this series of 1,000, acute abdominal pain was due to conditions that required neither surgical intervention nor hospitalization. Eleven of the 1,000 patients had an early missed diagnosis in the emergency clinic for which a subsequent operation was needed, and twenty underwent an operation which subsequent diagnosis showed was not required. All false-negative evaluations occurred in patients with early appendicitis or small bowel obstruction. Most false-positive results were due to acute infections of the female genitourinary tract in patients operated on to exclude appendicitis or a tubo-ovarian abscess. The following factors help identify the high risk patient with an acute surgical abdomen: (1) pain for less than 48 hours; (2) pain followed by vomiting; (3) guarding and rebound tenderness on physical examination; (4) advanced age; (5) a prior surgical procedure. The presence of these features demands careful evaluation and a liberal policy of admission and observation. White blood cell counts, body temperature, and abnormal abdominal roentgenograms may add confirmatory evidence but are not particularly helpful as screening devices.